1. Field of the Invention
The present invention is generally related to a reactive ion etch (RIE) barrier material used in semiconductor processing and, more particularly, to a method of using the reaction products of a novolac resin and either a polydiphenylsilazane or an organosilane compound in semiconductor or integrated circuit manufacturing processes.
2. DESCRIPTION OF THE PRIOR ART
In lift-off and/or multilayer processes, it is often necessary to employ a layer of film which is capable of withstanding an oxygen reactive ion etch (RIE). FIG. 1 shows the steps in a common trilayer process which employs a RIE barrier layer. First, a lift-off polymer 10, typically a solvent sensitive polymer, is applied to a substrate 12. An RIE barrier layer 14, such as hexamethyldisilazane (HMDS), silicon nitride (Si.sub.3 N.sub.4) or silicon dioxide (SiO.sub.2), is applied over the lift-off polymer 10. Finally, a photoresist layer 16 is applied to the top to complete the trilayer structure. The lift-off polymer 10, RIE barrier layer 14, and photoresist layer 16 can be applied by many well-known techniques including using a plasma tool or by spinning procedures. The photoresist layer 16 is then patterned by imaging and developing or by other suitable techniques. The pattern 19 is then transferred to the substrate 12 by first etching the RIE barrier layer 14 with CF.sub.4 and then etching the lift-off polymer 10 with O.sub.2 RIE. During O.sub.2 RIE, the photoresist layer 16 may erode away; however, the RIE barrier layer 14 remaining under the photoresist layer 16 will protect the underlying substrate 12. A blanket layer of metal 20 is then deposited by evaporation or by other suitable techniques, with the trilayer stacks serving as a stencil. Finally, the trilayer stacks are removed by dissolving the lift-off polymer 10 with an appropriate solvent.
FIG. 2 shows the process steps in a silylation technique. Unlike the trilayer process, the silylation technique only requires the deposition of a lift-off polymer 22 and a photoresist 24 on top of the substrate 26. The photoresist 24 is then patterned by conventional imaging and developing techniques. Before the pattern 29 is transferred to the substrate 26, the photoresist 24 is converted to an RIE barrier via silylation. The converted photoresist 24 then serves as a suitable stencil for patterning the substrate 26 in the same manner described in conjunction with the trilayer process, except that only an O.sub.2 RIE etch is required. As can be seen from FIG. 2, a blanket layer of metal 30 is deposited with the bilayer stack of photoresist 24 and lift-off polymer 22 serving as a stencil. Subsequently, the bilayer stack is removed by dissolving the lift-off polymer 22.
Heretofore, the RIE barrier layers used in the trilayer or silylation techniques have not been satisfactorily etch-resistant during RIE of the lift-off polymer using an O.sub.2 ambient. Consequently, portions of the RIE barrier material are etched away during this process and deposited as a residue in the etched areas 18 and 28 of FIGS. 1 and 2. Removal of this RIE barrier material accidentally deposited in the etched areas 18 and 28 requires further clean-up steps.
Spinning procedures allow uniform coats of a material to be applied to a substrate. It would be advantageous to apply an RIE barrier material by spin-on procedures. However, currently available spin on glasses which can be used as RIE barrier materials, have been found to have internal stresses which result in film cracking if they are spun on to a thickness of greater than 5000.ANG.. Hence, there is a need for a material which can be spun on a substrate to form relatively thick layers (e.g., 2.5 .mu.m) and used as an RIE barrier material.